Hi Bernado,
Just wanted to say a couple of things if I could help although not a sound expert or something, neither I have ever tried to replicate the exact sound of something.
If you want a specific sound that you have n your mind, it doesn't necessarily mean you have to use just one preset voice.
Especially on your SX900 you have 3 voices to combine.
That means you could choose a basic voice that sounds similar to what you want to achieve and afterwards you can add a second and a third voice in a much lower volume so to make your first voice sound brighter or more "bassy"(E.g the 2nd or the 3rd voice could be one octave down) and change the overall sound.
You can also set the voices that way that the first one will sound in the center, the other a little bit to the right etc.
Don't forget also to experiment with the tons of effects that there are inside the Mixer and the voice edit.
Also, you can use the Harmony with the Octave and set it on a much lower volume so the keyboard will automatically add the same notes that you are playing but in one octave lower
Another option is to set the release effect(something similar to the sustain button) for each voice individually in order to control the fade out of each voice.
The sustain button has a preset and long fade out.
That's why I propose the release effect.
As I can see, the keyboard player controls the fade out with his pedal.
But many of us don't use pedals on the keyboard,so....
Anyway this is pretty much the way that I edit the preset voices.
My goal is not to replicate a sound, but to archive something that sounds nice with a song, a style and the next set of voices I will use.
Maybe some ideas could be helpful to you in general
Chris is right about this kind of "Rhodes" sounds are inside the Electric Piano folders because we all recognize them in general as electric piano sounds.
To me, although "Rhodes" reminds me of an island, (
)
this type of electric pianos voices, sound like a mixture between different kinds of piano sounds combined with different kinds of vibraphone sounds in order to give that "metallic" sound.